Radiation therapy is employed for the treatment of tumor tissue in humans. Ions such as protons, helium ions, pions, carbon ions, or other types of ions can be employed for the radiation treatment. Radiation treatment with ions is characterized by the property that the penetration depth of the radiation into human tissue can be controlled more precisely than in other types of radiation treatment. This makes more precisely targeted radiation treatment of the tumor possible, and the surrounding tissue that is to be spared from damage can be better protected from the radiation.
The ions are accelerated to high energies in an accelerator system which, for example, includes a synchrotron or cyclotron, and are aimed in a beam at the body to be treated. The beam is deflected and controlled by a magnet system. Beam properties that are essential and relevant for safety are dependent on the settings of parameters at the system itself. These characteristics include, for example, the beam diameter, the beam position, and the energy of the beam. Such characteristics are measured, for instance, daily or weekly.
Monitoring the beam properties is performed with so-called phantoms. Such phantoms are irradiated with the particle beam, and the interaction of the particle beam with the phantom is measured or detected. This can be done, for example, by using photographic films that are exposed as a result of the irradiation by the particle beam, and allow conclusions to be drawn about the parameters of the particle beam. Detectors of other types, such as ionization chambers or thimble chambers, may also be employed.
Monitoring various beam parameters requires the use of many different phantoms. Until now, these phantoms have been individually and successively positioned manually relative to the beam. For each QA procedure, whichever phantom is needed is put in a defined spatial position relative to the beam so that for different phantoms, the positioning has to be performed each time and requires repetitive manual intervention. The expense in terms of time, labor, and cost is considerable.